Tie rod

ABSTRACT

The tie rod is designed to elongate when subjected to an overload in tension that is placed on the tie rod. A plurality of threads and a reduced diameter section on the tie rod elongated when subjected to a tension overload that exceeds the design parameters of the tie rod. The elongation of the tie rod is designed to provide a warning to the operator of the vehicle that the tie rod has been subjected to an overload and should be inspected and repaired as needed. The deformation and elongation of the tie rod absorbs energy and protects other components of the steering and suspension systems of the vehicle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/400,146filed Jan. 6, 2017, which claims the benefit of PCT/US15/41318 filed onJul. 21, 2015, which claims benefit of U.S. provisional patentapplication Ser. No. 62/027,478 filed on Jul. 22, 2014.

BACKGROUND OF THE INVENTION

The invention relates to link elements comprising at least twosubstantially rod-shaped link sections that are used in the suspensionof a vehicle. In particular the link elements are used to form a tie rodthat is used in the steering system of the vehicle to guide the wheelsto adjust to the desired steering angle.

Such link elements are crucial elements for the safe driving of a motorvehicle. The link elements are usually dimensioned with a high degree ofstiffness and failure safety. When used as tie rods, the link elementsoften have a defined failure safety or buckling stability. In thismanner a controlled buildup of energy in the event of a crash isappropriately controlled and adjacent components are protected againstdamage. In prior art tie rod applications the link elements have beendesigned to buckle when subjected to compression type loads on thevehicle suspension system. It is important that the link elements havean ability to accommodate a load that exceeds the design limitationwithout completely failing. It is important that the link elements notbecome separated so that the basic drivability and steerability of thevehicle can be maintained even in the event of a significant overloadcondition. It is also desirable for the driver of the vehicle to begiven an indication that the tie rod has been subjected to a significantoverload and that the steering system or vehicle suspension may becomedamaged due to the overload condition. It is important that thesignaling to the driver is sufficient to warn the driver that thesuspension and the steering system should be inspected and repaired.

In the current tie rod applications there is a lack of reliable systemsthat can effectively deal with an overload condition when the overloadis provided in tension on the link elements. There is also a deficiencyin tie rod systems that can progressively elongate under a tension loadto provide a warning to the driver that the steering and/or suspensionsystem has been subjected to an overload condition and needs to beinspected. There is further a lack of a tie rod assembly that canaccommodate an overload condition in tension without having the completefailure of the steering and/or suspension system.

Accordingly, there is a need in the art for a tie rod assembly that canaccommodate overload conditions in tension, provide a warning to thedriver of the vehicle when the overload condition has elongated the tierod while at the same time maintaining the tie rod in an operablecondition. The tie rod of the present invention has been developed toovercome these deficiencies of the prior art.

SUMMARY OF THE INVENTION

The tie rod of the present invention is designed to elongate whensubjected to an overload in tension that is placed on the tie rod. Aplurality of threads and a reduced diameter section on the tie rodelongated when subjected to a tension overload that exceeds the designparameters of the tie rod. The elongation of the tie rod is designed toprovide a warning to the operator of the vehicle that the tie rod hasbeen subjected to an overload and should be inspected and repaired asneeded. The deformation and elongation of the tie rod absorbs energy andprotects other components of the steering and suspension systems of thevehicle.

Other objects and advantages of the present invention will becomeapparent to those skilled in the art upon a review of the followingdetailed description of the preferred embodiments and the accompanyingdrawings.

IN THE DRAWINGS

FIG. 1 is a perspective side elevation view of the tie rod of thepresent invention.

FIG. 2 is a side elevational cross-sectional view of the tie rod.

FIG. 3 is a side elevational cross-sectional view of one of the rodcomponents of the tie rod.

FIG. 4 is a partial side elevational view of one end of the rod elementof the tie rod of the present invention.

FIG. 5 is a partial side elevational cross sectional view.

DETAILED DESCRIPTION OF THE INVENTION

The tie rod of the present invention is to be used with a vehicle. Thetie rod is used to control the steered wheels of the vehicle. Moreparticularly, the tie rod is designed to accommodate overload conditionsthat act in tension on the tie rod. The tie rod is designed to providean indication that a tension overload has been encountered by the tierod that compromises the proper function of the tie rod. The tie rod isalso designed to elongate under tension overload conditions to protectthe function of other components of the steering system. Other featuresand advantages of the invention will be more readily understood byreferring to the drawings in connection with the following description.

Tie rods of the prior art have a link section. The link section has athreaded section for connection to further link sections on one end anda ball joint on the other end that is connected to the suspension of thevehicle. Such tie rods of the prior art do not have an overload functionother than the simple buckling of the link in the event of compressionoverload in a direction towards the center of the vehicle. In such tierods, the compression overload condition causes a bend or curve in thetie rod that may or may not significantly impact the functionality ofthe tie rod. In addition, there is no damage indicator if the overloadforces are placed on the tie rod in the other direction, a tensionoverload, which is away from the center of the vehicle. In theapplication of a tension overload there is usually a complete failure ofthe tie rod before there is any indication of damage to the tie rod dueto an overload.

The tie rod of the present invention, which is shown in the attachedfigures, has been designed to provide a progressive indication that thetie rod has been subjected to an overload sufficient to cause damage tothe tie rod. When the overload reaches a predetermined magnitude, theoverload protection feature will allow the tie rod to elongate to anextent that will significantly impact the handling of the vehicle andgive the operator of the vehicle a clear warning that the tie rod andthe suspension of the vehicle need to be checked and repaired. The yieldof the material of the tie rod due to the overload condition results ina permanent change in the steering characteristics of the vehicle. Thetie rod 10 of the present invention has a rod 15 having a first end 17and a second end 19. A first plurality of threads 23 are positioned onthe first end 17 of the rod 15. A reduced diameter section 27 is on thefirst end 17 of the rod 15 adjacent the first plurality of threads. Therod 15 is cylindrical with a generally circular cross sectional shape.The reduced diameter section 27 is a groove 29 that is formed in the rod15. The groove usually has a semicircular shape and the width of thegroove extends in a direction towards the longitudinal axis of the rod15. The groove can also have a parabolic, elliptical or similar shape.The groove 29 has a depth that is from about 20% to about 40% of thediameter of the rod 15. The groove has a width that is from about 1diameter to about 3 diameters of the rod.

A link 31, having a chamber 33 positioned on one end, forms another partof the tie rod. The chamber 33 has a plurality of threads 37 positionedon the interior of the chamber 33. The link 31 and the chamber 33 aregenerally cylindrical and have a substantially circular cross sectionalshape. The plurality of threads 37 are disposed for engaging the firstplurality of threads 23, that are positioned on the first end of the rod15. The first plurality of threads 23 positioned on the rod 15 aredesigned to slip and deform when subjected to tension loads that exceedthe design limits of the tie rod. The tension load that exceed thedesign limits, is a load that will cause the rod 15 to move in adirection away from the link 31. If sufficient tension load is placed onthe tie rod 10, the reduced diameter section 27 is also designed toelongate. The elongation of the reduced diameter section happens as thefirst plurality of threads 23 have been subjected to the tension loadthat causes the first plurality of threads to slip and deform. The firstplurality of threads 23 and the reduced diameter section 27 allow thetie rod 10 to deform and elongate, and to absorb loads or energy intension over a longer distance. This results in the tie rod having theability to progressively handle tension overloads and to modify thelength of the tie rod progressively to provide a warning to the operatorof the vehicle that an overload has occurred.

The first end 17 of the rod 15 that is positioned in the chamber 33 isdesigned to be secured to the link 31. To assist in this connectionbetween link 31 and the rod 15 a second plurality of threads 25 arepositioned on the rod 15 on the opposite side of the reduced diametersection 27 from the first plurality of threads 23. The second pluralityof threads 25 are disposed on the end of rod 15 that extends thefarthest into the chamber 33. The second plurality of threadsthreadingly engage the plurality of threads 37 in the chamber. A lockingmeans, such as a glue, formed indentation or other means is used to keepthe rod 15 from disengaging from the chamber 33. It should berecognized, however, that other securing means, other than the secondplurality of threads, can be utilized to secure the rod 15 to the link31. As an example, a bore can be positioned to extend through thechamber 33 and the first end 17 of the rod 15. A pin could be positionedin the bore that extends through the chamber and the rod to secure therod to the link 31.

The first and second pluralities of threads that are positioned on thefirst end 17 of the rod 15 are buttress threads. A buttress thread has aload resisting flank 41 that can accommodate compression loads that actagainst the flank that are much higher than loads that act against thebuttress threads in the opposite direction. Such threads can accommodatelarge loads in one direction, but have a reduced capacity to handleloads in the opposite direction. In practice, the load that act againstthe flank 41 can be from about 1¼ to about 1¾ times larger than theforces that act on the threads in the opposite direction. In the presentinvention the load resisting flank is disposed toward the link 31 sothat compression loads in a direction along the rod 15 towards the link31 will be placed against the load resisting flank. This results in thefirst and second pluralities of threads being able to accommodatecompression loads that are much greater than the tension loads or loadsthat are directed in the opposite direction. The number of threads inthe first and second plurality of threads and the thrust angle of theflank 41 can be adjusted to change the overload parameters of the tierod. The first plurality of threads 23 will generally have a length lessthan 1 diameter of the rod 15 in threads and the second plurality ofthreads will have greater than 1.5 diameter of the rod 15 in threads.The thrust angle 45 of the flank 41 is usually from about 30° to about60° with respect to the longitudinal axis of the rod 15. The size of thereduced diameter section and the configuration of the first and secondplurality of threads can be adjusted to change the elongation parametersof the rod 15 in response to overloads in tension. This allows the tierod to be adjusted for different vehicles or driving conditions.

In most uses, the first plurality of threads 23 are caused to slip anddeform by the tension overload placed on the tie rod. Once the firstplurality of threads have elongated the reduced diameter section 27 willelongate if the overload is sufficiently large. The progressiveelongation results in a progressive compromise of the steering qualityof the vehicle that give the operator of the vehicle an increasingindicator that the tie rod has been subjected to an overload that hascompromised the effectiveness of the tie rod and the steering system.The deformation and elongation of the tie rod absorbs energy andprotects other components of the steering and suspension systems of thevehicle.

The above detailed description of the present invention is given forexplanatory purposes. It will be apparent to those skilled in the artthat numerous changes and modifications can be made without departingfrom the scope of the invention. Accordingly, the whole of the foregoingdescription is to be construed in an illustrative and not a limitativesense, the scope of the invention being defined solely by the appendedclaims.

We claim:
 1. A tie rod to transmit steering motion to the wheels of avehicle comprising: a rod having a first end and a second end; a firstplurality of threads positioned on the first end, the first plurality ofthreads being buttress threads having a load resisting flank; a linkhaving a chamber disposed on one end, the chamber having a plurality ofthreads that are disposed for engaging the first plurality of threads onthe first end of the rod, the first plurality of threads being designedto slip and deform when subjected to tension loads that exceed thedesign limits of the tie rod; and the load resisting flank disposedtowards the link wherein the first plurality of threads can accommodatecompression loads that are greater than the tension loads that can beaccommodated by the first plurality of threads.
 2. The tie rod of claim1 wherein the rod and link have a cylindrical shape with a circularcross section.
 3. A tie rod to transmit steering motion to the wheels ofa vehicle comprising: a rod having a first end and a second end, thefirst plurality of threads being threads having a bad resisting flank; afirst plurality of threads positioned on the first end; a secondplurality of threads positioned on the first end of the rod in adjacentspaced apart relationship to the first plurality of threads; and a linkhaving a chamber disposed on one end, the chamber having a plurality ofthreads that are disposed for engaging the first plurality of threads onthe first end of the rod, the first plurality of threads being designedto slip and deform when subjected to tension loads that exceed thedesign limits of the tie rod.
 4. The tie rod of claim 3 wherein thesecond plurality of threads are buttress threads that have a loadresisting flank disposed towards the link, the second plurality ofthreads being disposed to engage the plurality of threads in thechamber.
 5. The tie rod of claim 4 wherein the first and, secondplurality of threads are the same size and configuration.
 6. The tie rodof claim 1 wherein the first plurality of threads contains less than 1diameter of the rod in length of threads.
 7. The tie rod of claim 4wherein the second plurality of threads contains greater than 1.5diameter of the rod in length of threads.
 8. The tie rod of claim 1wherein the loath resisting flank has a thrust angle from 30% to 60%with longitudinal axis of the rod.
 9. The tie rod of claim 4 wherein theload resisting bank has a thrust angle from 30% to 60% with thelongitudinal axis of the rod.